Human listeners are facile at segregating the multitude of sound sources in the environment, and attending to a single sound stream. This process requires the integration of information across time and frequency. In order to examine the role of temporal processing the proposed psychophysical experiments employ the rarely used method of free response. For this procedure a masker is presented for several minutes and a target is presented at random times. The subject's task is to press a button whenever the target is detected. This procedure is well suited to the study of sound segregation because the presentation duration is long, mirroring "real world" situations. One question of primary interest addressed in the proposed experiments is whether the continuous nature of the method of free response increases the "cognitive load" on the subjects. A second primary issue is the development of a method that determines which "features" in time and frequency listeners rely on to detect a target in a competing environment. The method of free response has the advantage that button presses unfold over time, allowing the features to be extracted using reverse correlation methods to relate the time of button presses to the stimulus preceding it. The proposed experiments will evaluate the statistical reliability of the obtained features, a first step towards the useful application of this procedure. The proposed experiments and analyses are restricted to normal-hearing listeners. Should the method prove to be successful, the current results will provide a basic data set against which results from hearing-impaired listeners might ultimately be compared (not proposed). The brain mechanisms by which normal-hearing listeners are able to segregate sound sources (e.g., hearing a talker in a noisy environment) are not fully elucidated. Moreover, the ability of hearing-impaired listeners to segregate sound sources is impaired. The proposed research will contribute to the understanding of sound source segregation, with the potential of providing a basic understanding applicable to assistive hearing devices.